Lights for displays such as advertising, signage, signals or emergency signaling are typically of two types: incandescent and light emitting diodes (LED). Each of these types of lights has drawbacks that make them undesirable in certain applications. For example, although incandescent lights are readily available in various colors, and are able to emit bright light viewable from substantially any angle, incandescent lights also produce a substantial amount of heat in comparison to quantity of light emitted. Thus, the heat generation of incandescent lights wastes electrical power.
Alternatively, LEDs produce a relatively low amount of heat in comparison to the light emitted, and thus use substantially less electrical power as compared to incandescent lights. However, there are numerous restrictions on LEDs. For example, LEDs are typically circular or cylindrical; and it is not cost-effective for LEDs to be manufactured in an alternative shape that is better suited to a particular lighting application. Additionally, white light or multiple-color LEDs are not yet cost-effectively manufactured. LEDs also have relatively slow blink rates (e.g., 5 kHz) which causes a video display of sixty-four or higher levels of brightness to be distorted, for example, making it difficult or impossible to create animated displays with arrays of LEDs. Further, LEDs have a relatively narrow emission angle within which emitted light is effectively viewed—typically a maximum of 120 to 130 degrees.
FIG. 1 shows a pixel 2 of a prior art display (e.g., a billboard); pixel 2 is shown with a cluster of nine individual LEDs 4. Pixel 2 is commonly used where larger or brighter pixels are required; that is, by clustering LEDs 4 within pixel 2 and operating all LEDs 4 simultaneously, increased luminosity may be achieved. However, since LEDs 4 are round in shape, the illuminated area of pixel 2 (i.e., the sum of circular emission areas of LEDs 4) is less than the area of pixel 2 and therefore optimum pixel brightness is not obtained.